To the untrained eye, Buster is just a bunny, an innocuous cartoon character on American educational television. Each week the animated rabbit puts on his red backpack and trainers to visit a slice of real America - dropping in on a native Indian reservation in Wyoming, or maybe a Hispanic family in Los Angeles and sending a video postcard of the event to his friends.

The series, designed to show the diversity of the modern family to primary school children, is produced with $100m (£53m) of federal funding by the public television network PBS. It has a mandate to promote tolerance.

But then, Buster Baxter visited a farm in Vermont to learn about harvesting maple syrup. His hosts on Sugartime! were a lesbian couple and their children. Although the parents remained in the background - as they do during all of Buster's travels - their very appearance on children's TV was too much for the education secretary, Margaret Spelling.

Ms Spelling wrote to the president of PBS this week, saying: "Many parents would not want their young children exposed to the lifestyles portrayed in the episode."

The politician also asked the network to return federal funds used to make the episode, adding: "Congress's and the department's purpose in funding this programming certainly was not to introduce this kind of subject matter to children, particularly through the powerful and intimate medium of television."

PBS withdrew the offending episode, which had been scheduled for distribution to its 350 affiliates. However, the Boston station which produced it said it was going to make the episode available to broadcasters.

Buster is the latest fallen icon of TV Americana.

Last week, two conservative Christian organisations accused the cartoon SpongeBob SquarePants, an underwater sea sponge with two buckteeth, of conspiring to promote homosexuality to children. In the hugely popular television series, he holds hands with Mermaid Man as well as Barnacle Boy.

However, the yellow sponge managed to avoid the wrath of Christian conservatives until last week when it emerged that he was to star with other animation names, such as Big Bird and Barney, in a DVD remake of the hit We Are Family - a song intended to promote tolerance, which was to have been distributed to primary schools across the country.

Focus on the Family, a rightwing Christian group from Colorado, pronounced on its website: "While words like diversity and unity sound harmless ... enough, the reality is they are often used by gay activists as cover for teaching children that homosexuality is the moral and biological equivalent to heterosexuality."